Measurement and control systems and methods for electrosurgical procedures

ABSTRACT

An energy delivery system for use in performing a medical procedure is provided. The medical procedure can employ an energy source, the energy source can be connected to an energy delivering device via a transmission line. The energy delivery system can include a measurement system, the measurement system can be configured to sample an output signal generated by the energy source. The energy delivery system includes a control system, which includes a calibration unit. The calibration unit can be configured to generate a calibration signal. The calibration signal can have a magnitude and phase, wherein the magnitude and phase is representative of the output signal and the transmission line loss information. The energy delivery system can also include a control unit, the control unit being configured to receive the calibration signal and adjust the energy source as needed.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser. No. 11/827,266 filed on Jul. 11, 2007, the entire disclosure of which is incorporated by reference herein.

BACKGROUND Technical Field

The present invention relates to systems and methods for performing a medical procedure, wherein the medical procedure includes transferring energy from an energy source to a patient via a transmission line and, more particularly, maximizing the amount of energy transferred to a patient by compensating for the losses associated with the transmission line.

Description of Related Art

During most medical procedures in which an energy source is employed, the energy generated for the medical procedure is transferred to a patient via a transmission line. One example of a medical procedure employing an energy source is a microwave ablation surgical procedure. In a microwave ablation surgical procedure the energy generated may be a microwave having a frequency and a wavelength associated therewith.

During the microwave ablation surgical procedure, the microwave may be transmitted to the patient via a transmission line. Generally, the transmission line employed may have losses associated therewith that may be attributable to many factors. Factors that can cause transmission line losses include at least the following: the type of material used for the transmission line, the length of the transmission line, and the thickness of the transmission line.

It is known in the art that in order to maximize the amount of energy transferred from the source (microwave generator) to the load (surgical implement), the line and load impedances should match. If the line and load impedances do not match (i.e. impedance mismatch) a reflected wave may be created, which can generate a standing wave that can contribute to the power loss associated with the impedance mismatch.

During a typical microwave ablation surgical procedure, the impedance at the surgical site changes as the microwave ablation procedure progresses. This is because of tissue necrosis associated with the microwave ablation surgical procedure. Generally, the energy source may include an impedance matching circuit and/or tuner, which may be configured to compensate for these impedance changes at the surgical site. Conventional impedance matching circuits may include devices such as capacitors and inductors. However, because the energy source is generating microwaves, which have a much smaller wavelength than the length of the transmission line, it is often difficult to obtain accurate measurements for compensation of the impedance mismatch.

SUMMARY

A measurement and control system for use in performing a medical procedure is disclosed. The medical procedure may employ an energy source, wherein the energy source may be connected to an energy delivering device via a transmission line. In one embodiment, the transmission line may be a coaxial cable.

The measurement and control system may further include a measurement system, wherein the measurement system may be configured to sample an output signal, having a magnitude and phase that may be generated by the energy source. Additionally, the energy delivery system may include a control system, wherein the control system may include a calibration unit. The calibration unit may be configured to receive and store the loss information for the transmission line. Moreover, the calibration unit may further be configured to generate a calibration signal, wherein the calibration signal may have a magnitude and phase associated therewith. The magnitude and phase may be representative of the output signal of the measurement system and of the loss information for the transmission line.

In addition, the control system may include a control unit, wherein the control unit may be configured to receive the calibration signal and adjust the energy source in response to a value of the calibration signal.

The measurement system may be configured to include a directional coupler. The directional coupler may be configured to sample the output signal generated by the energy source.

In an embodiment, the transmission line loss information may be obtainable by storing the transmission line loss on a readable medium. In one embodiment, the readable medium may be a bar code. In an alternative embodiment, the readable medium may be a memory chip.

In another embodiment, the transmission line loss information may be obtainable via a calibration port on the energy source.

Further disclosed, is a method for measuring and controlling energy delivered to a patient from an energy source during a medical procedure. The energy source is connected to an energy delivering device via a transmission line, the method comprising the steps: a) determining losses associated with the transmission line and storing the loses in a calibration unit; b) generating an output signal from the energy source; c) sampling the output signal; d) measuring the sampled output; e) generating a calibration signal from the value of the loss information of the transmission line and the measured sampled output signal; and f) adjusting the output signal in response to the calibration signal.

In an embodiment, the step of sampling the output signal may be performed by a directional coupler.

In one embodiment, the step of determining losses associated with the transmission line may be performed by a network analyzer, wherein the loss information may be placed on the transmission line.

In yet another embodiment, the step of determining losses associated with the transmission line may be performed by a calibration port associated with the energy source.

In still yet another embodiment, the step of determining losses associated with the transmission line may be performed by a handheld device configured to perform a calibration test on the transmission line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of a measurement and control system according to an embodiment of the present disclosure; and

FIG. 2 is a schematic representation of a directional coupler of the measurement and control system of FIG. 1.

DETAILED DESCRIPTION

Detailed embodiments of the present disclosure are described herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure.

Referring to FIG. 1, a measurement and control system for use in performing a medical procedure, employing an energy source in accordance with the present disclosure is generally designated 10. System 10 may be employed in an electrosurgical energy source 20 or operatively connected to an electrosurgical energy source 20. Energy source 20 may be connected to an energy delivering implement or instrument 22 (e.g., an electrosurgical pencil, a microwave ablation antenna, etc.) via a transmission line 21 (e.g., a coaxial cable) or the like.

Measurement and control system 10 includes a measurement system 30 configured to sample and measure an output signal 40 generated by energy source 20. Each output signal 40 includes a magnitude and a phase. In one embodiment, measurement system 30 includes a dual directional coupler 50, hereinafter directional coupler 50, configured to sample each output signal 40, each forward voltage and reflected voltage generated by energy source 20.

Directional coupler 50 may be configured to operate like most conventional dual directional couplers known in the available art. For example, as seen in FIG. 2, directional coupler 50 may sample part of the generated energy output in transmission line 21. This may be accomplished by having two transformers (not shown), which are close enough to transmission line 21 such that energy passing through transmission line 21 electrically interfaces with the two transformers. Directional coupler 50 may have two coupled ports 50 a and 50 b, each having an isolation port 50 a′ and 50 b′, respectively (see FIG. 2). One type of dual directional coupler that may be employed with the present disclosure may be the MECA 722S series manufactured by MECA ELECTRONICS, INC. In one embodiment, directional coupler 50 may have one end connected to energy source 20 via transmission line 21 and a second end connected to energy delivering implement 22, also via transmission line 21. Directional coupler 50 may also be configured to be in operative communication with measurement system 30, to be discussed in greater detail below.

In one embodiment, a main line 50 e of directional coupler 50 may be designed for high power operation (large connectors), while coupled port 50 c may be designed for a SubMiniature version A connector (hereinafter referred to as “SMA”). Either isolation port 50 a′ or 50 b′ may be terminated with an internal or external matched load (typically 50 ohms). As commonly referred to in the art, and as used in the present disclosure, the term “main line” will refer to the section between an input port 50 c and transmitted port 50 d.

As mentioned above and as seen in FIG. 1, directional coupler 50 may be configured to be in operative communication with measurement system 30 so that the sample output signal 40 may be directed to measurement system 30. Thus, once output signal 40 is sampled via directional coupler 50, the sampled output signal 40 may be directed to measurement system 30, wherein the sampled output signal 40 may be measured.

Measurement system 30 may be configured to measure the sampled forward and reflected voltages 51 and 52, respectively, obtained by directional coupler 50 and generated by energy source 20. The power, the magnitude and the phase of the generated output signal 40 may be obtained or calculated from the measured forward and reflected voltages 51 and 52, respectively, by conventional algorithms to be discussed in greater detail below.

Measurement and control system 10 further includes a control system 60 having a calibration unit 61 configured to receive the magnitude and the phase of the generated output signal 40 from measurement system 30 and store loss information for transmission line 21. In an embodiment, the loss information for transmission line 21 may be obtained via a network analyzer 70 and placed on a machine readable medium 80 (e.g., a bar code). In an alternative embodiment, the loss information for transmission line 21 may be obtained via a calibration port 91 located on energy source 20, as will be discussed below.

Calibration unit 61 may be further configured to generate a calibration signal 62 having a magnitude and phase associated therewith. The magnitude and phase of calibration signal 62 may be representative of each output signal 40 and the loss information for transmission line 21.

Control system 60 further includes a control unit 63 configured to receive calibration signal 62 and adjust energy source 20 as needed.

In one embodiment, the forward, reflected, and/or load power portions of sampled output signal 40 may be directed to control unit 63 and the magnitude and phase portions of the sampled output signal 40 may be directed to calibration unit 61 of control system 60, as seen in FIG. 1. Calibration unit 61 may be configured to be in operative communication with control unit 63. Control unit 63 may be operatively and selectively connected to energy source 20 and may be configured to adjust energy source 20 as needed.

As seen in FIG. 1, energy source 20 may be any suitable type of energy source including but not limited to energy sources that may be employed for performing electrosurgical procedures which may include cryosurgery, microwave ablation surgery, laser surgery, electrocautery surgery, diathermy surgery and the like. Additionally, energy source 20 may be configured to generate any suitable type of waveform. The type of waveform generated will depend on the desires and/or needs of the user, which will depend on the type of electrosurgical procedure that is being performed.

Energy source 20 may include any and all switches, buttons, knobs, ports, scanners and the likes that will allow measurement and control system 10 to function as intended.

Energy source 20 may have a scanner 91 f in operative communication therewith. Scanner 91 f may be employed during calibration of transmission line 21 by network analyzer 70, wherein machine readable medium 80, placed on transmission line 21, is read by scanner 91 f.

With continued reference to FIG. 1, measurement and control system 10 includes a transmission line 21 connecting antenna 22 to directional coupler 50, of control system 30. Transmission line 21 may be made from any material medium or structure that can form all or part of a path for directing the transmission of energy. Additionally, transmission line 21 may be configured to function as conventional transmission lines known in the art. That is, transmission line 21 may be configured to transfer electromagnetic waves, acoustic waves, and/or electric power transmissions.

Transmission line 21 can be in the form of a wire, coaxial cable, optical fiber, electric power line, waveguide and the like. In one embodiment, transmission line 21 is a coaxial cable configured to selectively interconnect energy delivering implement 22 and energy source 20 or control system 30.

It should be noted that the energy values or parameters (e.g., power, magnitude and phase) of output signal 40 are valid at the output of energy source 20. Thus, in order to get a more accurate reading of the energy values or parameters that are delivered to the energy delivering implement 22, one would have to know the actual losses associated with transmission line 21. Once the loss information for transmission line 21 is determined, calibration unit 61 may be used to compensate for losses of transmission line 21.

The loss information for transmission line 21 may be determined by any suitable device and/or method. For example, the loss information for transmission line 21 may be determined via network analyzer 70. In one embodiment, network analyzer 70 may be an integral part of energy source 20 or alternatively, network analyzer 70 may be a separate handheld device or member 95 that is in operative communication with energy source 20. The network analyzer 70 may be used to perform a diagnostic test of transmission line 21.

Network analyzer 70 may function in a fashion similar to most conventional network analyzers that are known in the available art. That is, network analyzer 70 may determine the properties that are associated with transmission line 21, and more particularly, those properties that are associated with transmission line 21 that affect the reflection and/or transmission of output signal 40, such as, the characteristic impedance (Z_(O)) of transmission line 21.

Network analyzers that may be employed with measurement and control system 10 of the present disclosure may be of the type that are scalar network analyzers (hereinafter referred to as SNA), which can measure amplitude properties only. The network analyzers employed may also be of the type that are vector network analyzers (hereinafter referred to as VNA), which can measure amplitude and phase properties. Although both types of network analyzers may be employed with the present disclosure, for the remainder of the disclosure it will be assumed that the network analyzer 70 employed is a VNA.

As mentioned above, the loss information for transmission line 21 may be determined via a separate handheld device or member 95, which can be configured to perform a diagnostic test on transmission line 21. Once attached to transmission line 21, handheld device 95 may function similarly to network analyzer 70. As mentioned previously, handheld device 95 may be in operative communication with energy source 20 via an RF system and/or a port similar to port 91 d. In operation or use, once the loss information for transmission line 21 is determined, the loss information may be sent to and/or stored in calibration unit 61.

Employing a handheld network analyzer 95 has specific utility when energy source 20 is configured without a network analyzer 70 or the like therein. For example, for loss information testing performed on transmission line 21 at times prior to its actual use, and after the manufacture process, in the event that transmission line 21 has become defective or damaged (e.g., transmission line 21 may have been bent during shipping or may have become worn because of numerous uses), a user may employ handheld network analyzer 95 to perform the loss information test on transmission line 21 immediately prior to its use. After the calibration test is completed and the loss information for transmission line 21 has been determined, the new information can then be sent to calibration unit 61.

In an alternative embodiment, energy source 20 may be configured to include a calibration port 91. In this embodiment, calibration port 91 may be operatively and selectively connected to a network analyzer 70. Network analyzer 70 may be configured to perform the necessary loss information test and send the loss information for transmission line 21 to calibration unit 61.

As mentioned previously, the loss information for transmission line 21 may also be determined as part of its manufacturing process and placed on a machine readable medium 80, and placed on transmission line 21.

Energy source 20 may include a device, in the form of a scanner or reader 91 f, for reading a bar code and/or a memory chip. As shown in FIG. 1, reader or scanner 91 f may be in operative communication with calibration unit 61.

The information that may be stored on the readable medium or the memory chip may be any suitable type of information that may be used to calculate the losses associated with transmission line 21, for example, the type of cable employed, the length of the cable employed, and the date that the calibration test was performed. It will be appreciated by those skilled in the art that other types of information may be stored on the readable medium or the memory chip, and as such the preceding variables should not be construed as limiting.

Following the determination of the loss information for transmission line 21 via any of the aforementioned devices and/or methods, said loss information is sent to and stored in the calibration unit 61.

As seen in FIG. 1, calibration unit 61 may be in operative communication with measurement system 30. As mentioned above, calibration unit 61 may be configured to receive and store loss information for transmission line 21 and any and all other information that is deemed necessary to a user. Calibration unit 61 may also be configured to perform any necessary calculations, via an appropriate algorithm or the like, that can correct the magnitude and phase of output signal 40 generated by energy source 20 to compensate for the loss due to transmission line 21. Calibration unit 61 may be configured to generate a calibration signal 62 relating to the magnitude and phase of output signal 40 and loss information for transmission line 21. Calibration signal 62 may be employed to correct the impedance at the energy delivering device.

Control unit 63 may be configured to receive calibration signal 62 from calibration unit 61. Control unit 63 may be configured to analyze calibration signal 62 via at least one control loop 64. In one embodiment, control loop 64 may be configured to function similarly to other conventional control loops. That is, control loop 64 may include any and all sensors, control algorithms and actuators, which may be arranged in such a fashion so as to regulate the impedance at the energy delivering implement 22.

An example of how measurement and control system 10 functions and operates now follows. It is assumed, for purposes of this example, that the loss information for transmission line 21 has been determined during the manufacture process and transmission line via bar tag 80.

Prior to use of transmission line 21, a user can scan the loss information for transmission line 21 off of bar tag 80 via any of the aforementioned methods, such as bar code scanner 91 f. Once the loss information for transmission line 21 is scanned, the loss information may be sent to and stored in calibration unit 61, as described above.

As the electrosurgical procedure progresses, the tissue that is being treated by instrument 22 will cause the impedance at the surgical site to change, which may cause the load and line impedances to differ from one another. As used herein, “load impedance” is understood to mean the impedance actually experienced by output signal 40 and “line impedance” is understood to mean the impedance of transmission line 21. As mentioned previously, these mismatched impedances can result in the loss of electrosurgical energy between energy source 20 and instrument 22.

During the course of the electrosurgical procedure, the output signal 40 obtained and sampled by directional coupler 50, may be transmitted to calibration unit 61, wherein calibration unit 61 may perform the necessary calculations, via any number of algorithms or the like, to be discussed in greater detail below. Additionally, the phase associated with the total impedance, which includes the reactance (i.e., the imaginary part of the impedance) may be adjusted. Once the calculations are complete, calibration unit 61 may generate a calibration signal 62, which may include information regarding a magnitude and a phase for electrosurgical energy delivery. Calibration signal 62 may be directed to control unit 63 at which time control unit 63 sends the phase and magnitude information of calibration signal 62 through at least one control loop 64. After control loop 64 performs the necessary calculations, control unit 63 may adjust energy source 20 accordingly, via an output signal 62 a, to compensate for the loss of transmission 21 and/or the mismatched impedances, and to deliver appropriate electrosurgical energy to instrument 22. That is, energy source 20 will transmit an output signal or electrosurgical energy which is representative of and compensates for the impedance at the surgical site and the loss information for transmission line 21.

As mentioned previously, the impedance at the surgical site increases or decreases due to tissue decomposition, a value of the impedance at the surgical site is measured and relayed or communicated to calibration unit 60. After the impedance at the surgical site is received in calibration unit 61, calibration unit 61 will generate a calibration signal 62, via any of the aforementioned devices and/or methods. Calibration signal 62 will be representative of the impedance at the surgical site and the loss information of the transmission line 21.

One can measure the impedance at the surgical site via any suitable methods known in the available art. For example, the impedance at energy source 20 may be calculated. First, the forward and reflected voltages, V_(fwd) and V_(ref), respectively, are measured. Then, the voltage standing wave ratio (V_(swr)) may be calculated using the equation:

$V_{SWR} = \frac{V_{fwd} + V_{ref}}{V_{fwd} - V_{ref}}$

Then, the characteristic impedance of the source (Z_(O)) and the magnitude of the load impedance (Z_(L)) may be determined using the equation:

$\frac{Z_{L} - Z_{O}}{Z_{L} + Z_{O}} = \frac{V_{SWR} - 1}{V_{SWR} + 1}$

Those skilled in the relative art can appreciate that the phase may easily be determined via V_(fwd) and V_(ref). The magnitude and the phase of Z_(L) can then be communicated or relayed to calibration unit 60, which may be designed to adjust Z_(L) accordingly to compensate for the losses associated with transmission line 21. After all the necessary calculations have been carried out, signal 62 of control system 60 will be an accurate representation of the actual impedance at the surgical site.

The present disclosure also provides a method for measuring and controlling energy delivered to a patient from an energy source during a medical procedure. The energy source is connected to an energy delivering device via a transmission line, the method comprising the steps: a) determining losses associated with the transmission line and storing the loses in a calibration unit; b) generating an output signal from the energy source; c) sampling the output signal; d) measuring the sampled output; e) generating a calibration signal from the value of the loss information of the transmission line and the measured sampled output signal; and f) adjusting the output signal in response to the calibration signal.

As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense. It will be seen that several objects of the disclosure are achieved and other advantageous results attained, as defined by the scope of the following claims. 

1-14. (canceled)
 15. A measurement and control system for use in performing a medical procedure, employing an energy source, the measurement and control system comprising: a measurement system, including a directional coupler configured to sample an output signal generated by the energy source, the output signal having a magnitude and phase; and a control system operatively connected to the measurement system and including: a calibration unit configured to receive and store loss information for a transmission line, the calibration unit further configured to generate a calibration signal having a magnitude and phase that are representative of the output signal of the measurement system and of the loss information for the transmission line; and a control unit configured to receive the calibration signal and adjust the energy source in response to a value of the calibration signal.
 16. The measurement and control system according to claim 15, wherein the transmission line is a coaxial cable.
 17. The measurement and control system according to claim 15, wherein the loss information of the transmission line is stored on a readable medium.
 18. The measurement and control system according to claim 17, wherein the readable medium is one of a bar code and a memory chip.
 19. The measurement and control system according to claim 15, wherein the loss information for the transmission line is obtained via a calibration port on the energy source.
 20. The measurement and control system according to claim 15, wherein the loss information for the transmission line is obtained via a scanner.
 21. The measurement and control system according to claim 20, wherein the scanner is handheld.
 22. A measurement and control system for use in performing a medical procedure, the measurement and control system comprising: an energy source configured to generate an output signal; an energy delivery instrument; a directional coupler; a transmission line including a first portion directly coupled to the energy source and the directional coupler and a second portion directly coupled to the energy delivery instrument and the directional coupler, such that the output signal is unmodified as the output signal travels from the first portion to the second portion; a measurement system configured to sample the output signal generated by the energy source at the directional coupler; and a control system including: a calibration unit configured to receive the output signal and to generate a calibration signal based on the output signal and a loss information of the transmission line; and a control unit configured to adjust the energy source based on the output signal and the calibration signal.
 23. The measurement and control system according to claim 22, wherein the control system further includes: a network analyzer configured to determine the loss information of the transmission line and transmit the loss information to the calibration unit.
 24. The measurement and control system according to claim 22, wherein the measurement system is further configured to measure at least one of forward voltage or reflected voltage of the output signal to calculate at least one of forward, reflected, or load power. 